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<title>Ruby Procs: Ruby Study Notes - Best Ruby Guide, Ruby Tutorial</title>
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                <h1>Ruby Procs</h1>

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                  <strong>
                    <a href="/satishtalim/ruby_method_missing.html">&lt;Method Missing | </a>
                    <a href="/satishtalim/tutorial.html">TOC | </a>
                    <a href="/satishtalim/including_other_files_in_ruby.html">Including other files &gt;</a>
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                <p><i>Blocks are not objects</i>, but they can be converted into objects of class <strong>Proc</strong>. This can be done by calling the <strong>lambda</strong> method of the class <strong>Object</strong>. A block created with <strong>lambda</strong> acts like a Ruby method. If you don't specify the right number of arguments, you can't call the block.</p>

                <div class="column2">
                <!-- InstanceBeginEditable name="Code" -->
                <textarea name="code" class="ruby:nogutter:nocontrols" rows="15" cols="60">
                prc = lambda {"hello"}
                </textarea>
                <!-- InstanceEndEditable -->
                </div>

                <p><strong>Proc</strong> objects are blocks of code that have been bound to a set of local variables. The class <strong>Proc</strong> has a method call that invokes the block. The program <strong>p024proccall.rb</strong> illustrates this.</p>

                <div class="column2">
                <!-- InstanceBeginEditable name="Code" -->
                <textarea name="code" class="ruby:nogutter:nocontrols" rows="15" cols="60">
                # Blocks are not objects
                # they can be converted into objects of class Proc by calling lambda method
                prc = lambda {puts 'Hello'}
                # method call invokes the block
                prc.call

                # another example
                toast = lambda do
                  'Cheers'
                end
                puts toast.call
                </textarea>
                <!-- InstanceEndEditable -->
                </div>

                <p>The output is:</p>

                <div class="column2">
                <!-- InstanceBeginEditable name="Code" -->
                <textarea name="code" class="ruby:nogutter:nocontrols" rows="15" cols="60">
                >ruby p024proccall.rb
                Hello
                Cheers
                >Exit code: 0
                </textarea>
                <!-- InstanceEndEditable -->
                </div>

                <p>Remember you cannot pass methods into other methods (but you can pass procs into methods), and methods cannot return other methods (but they can return procs).</p>

                <p>The next example shows <i>how methods can take procs</i>. Example <strong>p025mtdproc.rb</strong></p>

                <div class="column2">
                <!-- InstanceBeginEditable name="Code" -->
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                =begin
                  You cannot pass methods into other methods (but you can pass procs into methods),
                  and methods cannot return other methods (but they can return procs)
                =end

                def some_mtd some_proc
                  puts 'Start of mtd'
                  some_proc.call
                  puts 'End of mtd'
                end

                say = lambda do
                  puts 'Hello'
                end

                some_mtd say
                </textarea>
                <!-- InstanceEndEditable -->
                </div>

                <p>The output is:</p>

                <div class="column2">
                <!-- InstanceBeginEditable name="Code" -->
                <textarea name="code" class="ruby:nogutter:nocontrols" rows="15" cols="60">
                >ruby p025mtdproc.rb
                Start of mtd
                Hello
                End of mtd
                >Exit code: 0
                </textarea>
                <!-- InstanceEndEditable -->
                </div>

                <p>Here's another example of passing arguments using <strong>lambda</strong>.</p>

                <div class="column2">
                <!-- InstanceBeginEditable name="Code" -->
                <textarea name="code" class="ruby:nogutter:nocontrols" rows="15" cols="60">
                a_Block = lambda { |x| "Hello #{x}!" }
                puts a_Block.call 'World'
                # output is: Hello World!
                </textarea>
                <!-- InstanceEndEditable -->
                </div>

                <p class="post-note"><strong>Fabio Akita</strong> a Brazilian Rails enthusiast, also known online as "AkitaOnRails", wrote this exclusive article on <strong><a href="/blog/2007/11/30/akitaonrails-on-anatomy-of-ruby-blocks/closures/">Ruby Blocks/Closures</a></strong> for the rubylearning.github.io members like you. Do read, after you have gone through this lesson.</p>

                <p style="background-color: #FAFAFA; padding: 5px; margin-top: 20px; font-size: 65%;"><strong>Note</strong>: The Ruby Logo is Copyright (c) 2006, Yukihiro Matsumoto. I have made extensive references to information, related to Ruby, available in the public domain (wikis and the blogs, articles of various <span style="font-weight: bold;" title="Click Gurus on the menu above">Ruby Gurus</span>), my acknowledgment and thanks to all of them. Much of the material on <a href="/">rubylearning.github.io</a> and in the course at <a href="http://rubylearning.org/">rubylearning.org</a> is drawn <strong>primarily</strong> from the <strong>Programming Ruby book</strong>, available from <a href="http://pragprog.com/book/ruby3/programming-ruby-1-9-2-0">The Pragmatic Bookshelf</a>.</p>

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                  <strong>
                    <a href="/satishtalim/ruby_method_missing.html">&lt;Method Missing | </a>
                    <a href="/satishtalim/tutorial.html">TOC | </a>
                    <a href="/satishtalim/including_other_files_in_ruby.html">Including other files &gt;</a>
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